Lc Tank versus half-wave antenna

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Jagau posted this 08 May 2018

 

A comparison of the technical aspects on the LC tank circuit circuit and a half-wave antenna.

In this thread I will refer often to these two figures

  

Fig. 1 is a well-known figure of all, it is a LC tank coil consisting of a coil and a capacitor.

The fig.2 is a half wave antenna consisting of 2 times ¼ wave which makes us a total length of lamda divide by 2.

 

When you compare the two figures you can see very quickly that there is a very big difference both physical and technical between the two, I explain myself.

The 4 main parameters to compare are: directivity, polarization, impedance and frequency.

For the coil of Fig.1 a tank coil, when the coil is cut to a certain length, there is resonance at a certain frequency and the fact of winding increases its inductance. It is helped by a capacitor to more precisely reach the desired frequency. The radiation of a coil is at its maximum in its center ie inside the coil so its directivity is at its maximum when it is located on the top of another coil and not at the inside, in order to have a maximum magnetic exchange.
As an example in the case of the Don Smith generator L1 is on the top of L2 coil and not on the inside. The polarization of a tank coil is infinite resonance and is governed by the rule of the right hand RHR and its impedance is infinite at resonance.

Regarding our fig 2 the antenna is not rolled like a coil but straight, it will resonate at the cutoff frequency and its directivity is omnidirectional and the power transmitted. Moreover the end of the quarter wave should never be connected to any other electrical component otherwise we would have an mismatched antenna , instead of having an impedance of 73 ohms, as we should have, it will be a mismatch with a stationary wave ratio very high SWR and no power radiate. For an antenna of this type one can have a vertical or horizontal polarization, the polarization is determined by the polarization of the antenna of the transmitter, one must have the same polarisation to the receiver to receive a signal.

After having examined these concepts on the LC tank and the half-wave antenna, we can conclude that they do not have many related links except that of their frequencies. One can not compare a tank coil to an antenna, the point of attachment of a half-wave antenna is crucial and that is what makes its impedance. The voltage in an LC tank is provided in both ends giving it an infinite resonance impedance. In a half-wave antenna the top part is the radiator and the bottom part is the ground plane and they could not be join.

Only an analogy on the word transmitter and receiver may be appropriate. Don Smith used rather the concept reactant coil and réactor coil it is much more precise.

To be continued, I hope I did not discourage you too much

Jack

 

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Chris posted this 08 May 2018

Jack, this is a fantastic Thread! Great resource!

Antenna's and Coils as you point, have quite different characteristics, however, follow the same basic principles. In Antenna's, Near Field and Far Field are phenomena that is supposed to define some Field Characteristics:

 

However, there is no real theory I have found on this in Inductors. Inductors Radiate, but the Field effects are only ever talked about in an Induction scenario, which could be equated to the Near Field effect, equal and opposite.

The Mr Preva Experiment does prove that there is at least Near Field and Fresnel Effects.

Jack, a great post, thumbs up an Favorited from me!

   Chris

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Jagau posted this 08 May 2018

OK well as you can see in you image fresnel equation predict  Te and Tm this the first who predict that.

about near fear its apply only to inductor i think.

well my post was just my point of view it can be discussed anyway.

have  a nice day

Jack

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Chris posted this 09 May 2018

Hey Jack,

NF Fields are most commonly associated with Antenna's. It is an interesting area to study.

 

Below, audio starts at: 1:43

 

All very interesting videos.

   Chris

Jagau posted this 09 May 2018

Yes indeed very interesting video to study.

I'm staying with the idea that it was magnetic near field of a coil you told me about RF near field

I'm sorry I was not talking about the same thing,

indeed radio frequency near field is different from the magnetic near field near the coil, I'm sorry.

Jack

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Chris posted this 09 May 2018

Hey Jack,

Apologies, I agree with your post. I strayed a little off topic.

   Chris

 

Chris posted this 09 May 2018

Hi Jack,

I know you already know this, but for all readers I would like to continue your Antenna concept.

An Antenna, can couple in the Near Field, a Current can be induced as we would conventionally see:

 

These theories, Near, Freznel and Far Fields are important concepts and much of our Wireless Communications technologies are based on these theories.

 

The above video is very important! A HUGE amount of very important information!

NOTE: The mention and statement of the Magnetic Field: 1 + 1 = 4

 

Also, this field of Electromagnetic Theory aligns very closely to Optics, especially what Tom Bearden was talking about, Phase Conjugate Mirror, PCM.

Its not to hard to see, the litraure does show ideas and concepts:

In LLC resonant converter, the integrated transformer with high leakage inductance is preferred to get high power density by eliminating the series resonant inductor. However, high leakage inductance results from stray magnetic field between primary winding and secondary winding, which brings near-field effect and severely impacts on near-by components. In this paper, the mechanism of near-field effect is discussed and the model of the integrated transformer applied in LLC converter is built. Furthermore, this paper takes the metal case of power supply for example to analyze the near-field phenomenon. Based on an 185W power supply, both simulation and experiment results are carried out. The near-field phenomena get well explanation.

IEEE - Analysis on near-field effect caused by stray magnetic field of integrated LLC transformer

 

Some interesting tech is starting to emerge!

   Chris

Chris posted this 09 May 2018

@All - How is this for coincidence:

 

   Chris

Zanzal posted this 09 May 2018

However, there is no real theory I have found on this in Inductors. Inductors Radiate, but the Field effects are only ever talked about in an Induction scenario, which could be equated to the Near Field effect, equal and opposite.

Great topic guys. I definitely need to know more about near and far field. Was reading something yesterday where the author claimed transformers work primary through the near field. While I am not sure I trust this author since he was very much against Tesla's claims that his wireless power transfer did not use Transverse EM waves, he did provide some good general info about near and far field:

http:// www.capturedlightning.com/frames/Non-Herzian_Waves.html

There is one way we can maybe test this. Assuming that the near field is blocked by a faraday cage we could surround the primary of a transformer with thick aluminum foil. If the power is being transferred as a result of the near field and if the near field is blocked by the foil then the secondary should be largely dead. Personally, I suspect the transformer will still work fine, but then if that turns out to be true, how do I know I really blocked the near field. Thoughts?

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Chris posted this 09 May 2018

Hey Zanzal,

I still have a lot to learn in this area. I find this very interesting.

Assuming that the near field is blocked by a faraday cage we could surround the primary of a transformer with thick aluminum foil. If the power is being transferred as a result of the near field and if the near field is blocked by the foil then the secondary should be largely dead.

Initially I thought this also. I may be wrong, but I believe the Near Field is unshieldable:

 

To reference, Floyd Sweet said the same thing:

Of all the known fields - electric, magnetic, gravitational and motional E-field, the only ones incapable of being shielded are the induced motional E-field and the gravitational field.

 

Note the stated fact about Energy being the the Square of the Field.

 

The underlying principal (forget Millikan’s experiment) has been derived in that magnetic effects vary on the square of the current.

Floyd "Sparky" Sweet - The Space-Flux Coupled Alternator

 

The field energy is proportional to the square of the amplitude of the total electromagnetic field. As a result, the simple addition of the energy fields of the total field can be many times the energy of the initial fields separately. This property of the electromagnetic field is non-additivity of the energy field

Andrey Melnichenko - Transgeneratsiya electromagnetic field energy

 

I found this very interesting also:

 

So all the energy is stored in the Field, and this storage phase is around the Quarter Wavelength! This is a fantastic piece of information! Why, because it gives insight to the already known Quarter Wavelength requirement that we know of.

   Chris

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Jagau posted this 09 May 2018

Hey Zantal excellent comment.

Nicholson should have read Maxell's book to understand what Tesla was saying. Moreover, Maxwell's ideas on the action of remote charges were poorly received in the scientific world at that time, he had to back down to retreat on what he had discovered so as not to displease.

In the paragraph  ''charge and field'' it's simply bad knowledge, I just do not agree with what Nicholson wrote. Who is he, have you ever heard of him?

Dr. Nicolas Tesla with more than 700 patents to his credit did not only joke about writing books he acted and unfortunately those who get involved pay the price.

Jack

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